As a kind of lightweight aggregate, ceramsite can be used instead of ordinary sand and stone to prepare lightweight aggregate concrete. The ceramsite has a wide application in departments of construction, environmental protection, metallurgy, chemical industry, petroleum, agriculture, etc. Especially in the aspect of water treatment, the ceramsite, as a filler for water treatment, has been used more and more widely. The calcination of ceramsite with the addition of sludge was first proposed by Nakouzi et al., wherein the ceramsite was obtained by pelletizing and calcination by using the sludge as a raw material, and adding an appropriate amount of auxiliary materials.
Shells, oysters, etc., are common marine products. At present, the development and utilization of seashell products generally focuses on processing the edible parts. While using the edible parts, a large number of shells are produced. Most of these shells are discarded, and only a small part of these shells are used for making feed. The shells discarded as garbage are piled up for a long time. The residual organic matters occupy space, decay and stink during the long-time storage process, which endangers the health of residents and causes serious pollution to the ecological environment. In recent years, shell products are increasing rapidly with the continuous expansion of the scale of aquaculture in coastal cities. It receives much concern as how to protect the ecological environment, control shell pollution, develop and utilize the large number of cheap and discarded shell resources, recycle and turn the garbage into treasure.
At present, some ceramsite products have been prepared by using seashell products as raw materials. A Chinese patent with the application number of 2013103846370 (Application Date: Aug. 29, 2013), “Method for Preparing a Shell Ceramsite Biocarrier”, discloses a shell ceramsite biocarrier and a preparation method thereof. The biocarrier is a ceramsite sintered with shells, clay and a high temperature binder, and the prepared shell ceramsite biocarrier has rich foam structures, and is beneficial to the propagations of various microorganisms. But the cost is high, and the treatment effect on wastewater contaminated with heavy metals is limited. A Chinese patent with the application number of 2014103348562 (Application Date: Jul. 14, 2014), “Method for Producing Ceramsite, Ceramsite, and Application of Ceramsite”, discloses a method for producing ceramsite. In the method, fly ash, sludge, clay and oyster shell powder are used as raw materials, wherein the sludge is subjected to a pressure filtration and a natural drying treatment in water works, and a water content of the sludge is 45-60%. The ceramsite is achieved by granulating and sintering the above raw materials at a high temperature, which is beneficial to reduce the consumption of the clay. The obtained ceramsite has good ability to adsorb pollutants, but has low strength and low bio-immobilization efficiency. A Chinese patent with the application number of 2015104033827 (Application Date: Jul. 11, 2015), “Ceramsite Aerated Block Added with shell powder” discloses a ceramsite aerated block prepared by shell powder, ceramsite, fly ash, quicklime, cement, aluminum powder, gypsum powder, sludge, calcium lignosulfonate, iron powder, nano aluminum oxide, carbon black, absolute ethanol and water. The block is not easy to crack, saves natural resources, but cannot absorb harmful substances.